1. Field of the Invention
The present invention is generally related to a marine drive unit which is able to absorb energy during an impact situation and, more particularly, to a marine propulsion system which provides at least two energy absorption portions which are cooperatively configured to experience an acceptable amount of damage during low speed collisions and react to higher speed collisions with a separation of the propulsion unit from the hull of a marine vessel without seriously breeching the hull.
2. Description of the Related Art
Many different types of marine propulsion systems are well known to those skilled in the art. Some of these propulsion systems are provided with shock absorbing capability through the use of hydraulic or pneumatic cylinders. Typically, this technique is used in conjunction with outboard motors or sterndrive systems. However, some other types of marine propulsion devices utilize techniques that absorb energy in other ways. These other techniques can involve the use of energy absorbing devices or breakaway systems.
U.S. Pat. No. 1,943,288, which issued to Chandler et al. on Jan. 16, 1934, describes an outboard propeller and rudder mounting device. The primary object of the system is to provide a highly efficient, practical, and novel design of a drive unit that is adapted for connection with the driveshaft of a motor or engine disposed within the hull of a boat. A further object of the device is to provide a drive unit with a swingable propeller mounting permitting a laterally upward movement of the propeller while running, thus permitting the propeller to function in relatively shallow water in conjunction with a rudder support and a rudder which is mounted and adapted for control adjustment independent of the propeller mounting.
U.S. Pat. No. 2,093,454, which issued to Kistler on Sep. 21, 1937, describes a method of producing an aerogel material. Whenever a colloidal solution is precipitated, the product formed is usually defined as a gel. It is distinct from the precipitates from crystalloidal solutions by containing large quantities of the solvent in a soft gelatinous mass, usually microscopically heterogeneous and presenting some rigidity.
U.S. Pat. No. 2,681,029, which issued to Canazzi on Jun. 15, 1954, describes a propulsion drive unit for boats. It relates to improvements in boat drives wherein a propulsion unit of the drive is secured to the outboard side of a boat and is operably connected to a motor and to operating controls within the boat. It provides a small, compact, quiet and efficient reversible and steerable propulsion drive unit for boats to provide an attractive appearing housing which encases a drive mechanism, a cooling system for the drive mechanism and reversing and steering mechanism so that by forming a single large installation hole in a boat the drive unit may be readily installed and operably connected to a motor, to cooling and exhaust conduits of the motor, and to steering and reversing controls in the boat.
U.S. Pat. No. 2,917,019, which issued to Krueger on Dec. 15, 1959, describes a propeller housing attachment. It provides an improved insertable motor mounting structure for a boat in combination with the protection of a motor boat propeller and its operating mechanism. It is concerned with an improved insertable reinforcing structure for a motor mounting and the protection, removal and replacement of a boat propeller in combination with an automatic ignition cutoff when the propeller housing and its associated driveshaft are disengaged from the main driveshaft housing and its associated driveshaft. In the operation of outboard motor craft using a propeller drive there is usually provided at some point of the drive a shear pin or key which is automatically broken when the propeller hits a snag or is stopped suddenly by some obstructing force. This shear pin must be replaced by dismantling the structure and replacing the broken shear pin. This dismantling of a simple outboard motor is usually not difficult, if tools are available, as the motor can be dismounted or the propeller tipped out of the water within reach of the hands. However, with larger permanently installed motors, where the propeller housing and its associated drive are a permanent attachment, the replacement of the shear pin or repair of a damaged propeller is more difficult and usually requires breeching of the craft for necessary repairs.
U.S. Pat. No. 3,151,597, which issued to Larsen on Oct. 6, 1964, describes an impact absorbing means for a marine propulsion device. It relates to structures which carry a propeller which are normally submerged during operation and which are accordingly subject to impact against a submerged obstacle. The striking of submerged obstacles results in impact loading of the unitary assembly and a change in the direction of momentum of the unitary assembly evidenced by the upward swinging of the unitary assembly about its horizontal pivotal mounting. The invention involves the provision of bumper means including a body of resilient material for extending the time interval during which impact occurs, thereby reducing the magnitude of the resultant impact force, and thereby also protecting the unitary assembly.
U.S. Pat. No. 3,903,827, which issued to Marcil on Sep. 9, 1975, describes a non-heeling hull assembly. A boat including a hull having a deck and bottom, a sail carrying mast, and a keel structure, with the mast and keel being pivotally supported from the hull and so operatively connected by hydraulic or mechanical means that when the boat is wind driven the mast may tilt to port or starboard with concurrent pivoting of the keel structure in an opposite direction. Pivoting of the mast and keel structure is independent of the hull, and the hull remaining in a non-heeling position when the boat is wind driven at a substantial rate is described.
U.S. Pat. No. 5,007,868, which issued to Fry on Apr. 16, 1991, describes a replaceable skeg for a marine propulsion device. It includes a tapered dovetail tongue and groove joint between the top of the skeg and lower portion of a gear case housing on the marine propulsion device. When the skeg is hit by an underwater obstruction it will fracture at the joint and break away, leaving the lower portion of the gear case housing in tact and undamaged in which another skeg can be installed thereto.
U.S. Pat. No. 5,018,997, which issued to Guptill on May 28, 1991, describes a skeg protector. It is mounted on the leading edge of the skeg of a boat motor. The protector is in the form of a channel of stainless steel fitted on the skeg with the base of the channel spaced forwardly of the leading edge of the skeg. A rubber strip extends along the inside of the channel.
U.S. Pat. No. 5,277,632, which issued to Davis on Jan. 11, 1994, describes a boat motor replacement skeg. It is thin and flat and has a cavity formed in one of its edges. The replacement skeg is slid over the stub which remains after the original skeg is broken off and is fastened to the skeg stub with silicon sealant and rivets.
U.S. Pat. No. 5,361,715, which issued to Kiedaisch et al. on Nov. 8, 1994, describes a marine dock fender contact surface attaching boss. The fender for absorbing the impact between converging bodies includes a supporting surface, a plurality of bosses and an energy absorbing member. The plurality of bosses protrudes from the supporting surface at spaced locations. Each boss has an outer perimeter. The energy absorbing member surrounds the outer perimeter of each boss so that each boss absorbs vertical and horizontal shear forces within the energy absorbing member.
U.S. Pat. No. 6,315,623, which issued to Hedlund on Nov. 13, 2001, describes a drive means in a boat. The drive assembly includes a propeller shaft housing which projects downwards on the underside of the bottom of the boat and is connected to a drive unit, arranged on the side of the boat, via members which, in the event of a load acting on the housing, for example in the event of grounding, bring about controlled separation of the housing from the drive unit and the bottom of the boat.
U.S. Pat. No. 6,966,806, which issued to Bruestle et al. on Nov. 22, 2005, discloses a replaceable leading edge for a marine drive unit. A marine propulsion device is made of first and second portions which are removably attachable to each other. The second portion is the leading edge portion of the nose cone and the driveshaft housing. It can also comprise a portion of the skeg. The second portion is configured to crush more easily in response to an impact force than the first portion. This can be accomplished by making the second portion from a different material than the first portion, which can be aluminum, or by providing one or more crush boxes within the structure of the second portion to cause it to yield more quickly to impact force and thus protect the first portion which is the more critical structure of the marine device.
U.S. Pat. No. 7,435,147, which issued to Eichinger on Oct. 14, 2008, discloses a breakaway skeg for a marine propulsion device. The device is provided with a breakaway skeg having first and second attachment points. The first and second attachment points are configured to result in the second attachment points disengaging from a gear case or housing structure prior to the first attachment point. The attachment points can comprise open or closed slots and, when an open slot is used for the first attachment point, it can be provided with a first edge along which a first pin can exert a force along a preselected angle in response to an impact force on the skeg. The arrangement of attachment points allows a reaction force at the second pin to be predetermined in a way that assures the detachment of the skeg from the housing structure prior to the detachment of the housing structure from another structure, such as the boat hull, or transom.
U.S. patent application Ser. No. 11/970,132 (M10158), which was filed by Mihelich et al. on Jan. 7, 2008, discloses a marine drive with a breakaway mount. A marine drive has a breakaway mount mounting first and second sections of the drive and breaking away in response to a given underwater impact against the second section to protect the first section and the vessel. It is particularly intended for use in conjunction with marine propulsion devices that extend downwardly, with a generally vertical driveshaft, through the hull of a marine vessel.
U.S. patent application Ser. No. 11/970,141 (M10164), which was filed by Eichinger on Jan. 7, 2008, discloses a torsion bearing breakaway mount for a marine drive. A marine drive has a breakaway mount provided by hollowed out threaded fasteners mounting first and second sections of the drive and breaking away in response to a given underwater impact against the second section to protect the first section and the vessel. The threaded fasteners are arranged in a bolt circle and positioned in a way that allows a marine drive unit to be cleanly separated from the marine vessel without adversely affecting the integrity of the marine vessel. It is particularly intended for use in marine propulsion systems that incorporate a generally vertical driveshaft extending downwardly through the hull of the marine vessel, but can be used in other types of drive units.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
As described above, many different types of energy absorbing devices and systems are known for use in conjunction with marine vessels. However, as will be described in greater detail below, the known types of devices typically exhibit disadvantages in their use. For example, although certain types of resilient bumpers can be applied to the leading edges of marine drive units to absorb energy, they are limited in the maximum amount of energy that can be withstood before complete destruction of a marine drive unit occurs in a way that can sink the marine vessel. Other devices are configured to cleanly break away from a marine vessel to avoid catastrophic damage to the vessel in the event of an impact at relatively high speeds. However, if devices of this type experience a relatively low energy collision with underwater obstructions, a premature breaking away of the drive unit can be unnecessarily expensive. Another concern that exists when employing energy absorbing devices is the effect on passengers of the marine vessel during the brief time when the energy is being absorbed by the device. Any device that involves the sudden deceleration of a moving marine vessel can also cause the passengers of the vessel to be adversely affected since, in most cases, those passengers do not wear safety harnesses while traveling on the marine vessel. Therefore, unlike land vehicles, the passengers are not equipped with devices that stop their forward movement in the event that the marine vessel is suddenly decelerated.
It would therefore be significantly beneficial if a marine vessel could be provided with a system that addresses the various problems that occur when a marine vessel experiences an impact against a stationary obstruction at various different speeds.